Electrostatography is best exemplified by the process of xerography as first described in U.S. Pat. No. 2,297,691 to C. F. Carlson. In this process, the photoconductor is first provided with a uniform electrostatic charge over its surface and is then exposed to image wise activating electromagnetic radiation which selectively dissipates the charge in illuminated areas of the photoconductor while the charge in the non-illuminated areas is retained thereby forming a latent electrostatic image. This latent electrostatic image is then developed or made visible by the deposition of finely-divided electroscopic marking particles referred to in the art as “toner”. The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the latent electrostatic image. This powder image may then be transferred to a support surface, such as paper. The transferred image may subsequently be permanently affixed to the support by heat fusing. Instead of forming a latent image by uniformly charging the photoconductive layer and then exposing the layer to a light and shadow image, a latent image may be formed by charging an insulating or photoconductive insulating member in image configuration. The powder image may be fixed to the imaging member if elimination of the powder image transfer step is desired.
Several methods are known for applying an electrostatic charge to the photosensitive member, such as the use of electron-emitting pins, an electron-emitting grid, single corona-charging structures, scorotrons and multiple dicorotron wire assemblies. In recent development of high speed xerographic reproduction machines where copiers can produce at a rate of up to or in excess of two to three thousand copies per hour, the need for several reliable corona charging assemblies in order to utilize the full capabilities of the reproduction system is required. Also, with the advent of color copiers where several corona-charging stations are needed, the requirement for dependable corona or scorotron assemblies for depositing an electrostatic charge is essential.
Generally, in electrostatographic or electrostatic copy processes, a number of corotrons, dicorotrons or scorotrons are used at various stations around the photoreceptor. For example, they are or may be used at the station that places a uniform charge on the photoreceptor at a transfer station, at a cleaning station, etc. In today's complex marking apparatus, it is important that all charging units (or corotrons) are in perfect working order since corotron malfunction or damage can easily render the entire electrostatic copying process non-functional. Maintaining each corotron unit in perfect working order from shipping to insertion in the machine is essential to the proper functioning of these complex marking systems or copiers.
In shipping, these corotron cartridges sometimes referred to as customer replacement units, the corotron or scorotron is housed in a protective guide, this guide is needed both to protect the corotron during shipping and to aid the customer in the insertion of the corotron cartridge into the electrophotographic marking apparatus. Some current protection guides have locking features or designs intended to retain the corona cartridges in place during shipping and insertion into the electrostatic marking apparatus. Since corona cartridges are comparatively expensive and require special care to avoid damage, attention to these protection guides is essential. While these prior art locking features generally will retain the cartridge under ideal conditions, if sufficient force is applied, or if the protection guide is turned on end, the cartridge will release from the guide and fall out. This is possible during shipping and during handling or while inserting the cartridge into the electrostatic marking machine. Once the cartridge falls free of the protective guide, there is great potential for damage.